Recently picked up a 68 Belvedere with a 318 and it runs great except one thing, every time I hit 25 - 30 mph in D it kicks down into passing gear. I have tried adjusting the kickdown linkage using the open throttle method and there was no real change. After I made the adjustment, it did shift into third but only at 50 mph and with the throttle wide open. As soon as I let off of it, she kicked back down into passing gear. The shift linkage in the column is a little loose, but D2, D1, and R work just fine. It shifts smoothly from first to second, but as soon as I hit what should be third it slips into passing gear. At this point I am open to any advice. I thought that maybe investing in a Lokar cable may fix it, but I don't know at this point.
I'm a little confused. Your Torqueflite only has 3 speeds, 1st, 2nd, & 3rd. So after it shifts to 2nd it shifts back to 1st? Is that what it is doing?You need to look at this GREAT article:http://www.allpar.com/mopar/transmissions/torqueflite-tom-hand.html
Yes that is what it does, and I thought it was the kickdown linkage at first. All the linkage was put in wrong. But fixing it didn't change anything.
Looking at a '69 Dodge factory manual, Torqueflite troubleshooting section, the number one cause of the erratic operation you describe is "Incorrect throttle linkage adjustment". If it isn't that, there are dozens of other potential problems: low fluid level, hydraulic pressures too high or too low, governor sticking or leaking, oil filter clogged, valve body malfunction, clutches or servos sticking or not operating, faulty oil pump, kickdown band out of adjustment... sorry it's awful hard to diagnose this.
I think we have it narrowed down to either the valve body or the governor. I am gonna get it up on a lift this saturday and take a good look at it then. I will let you know what, if anything, I discover.